The art and science of aligning teeth and modifying the growth and form of the human face, known as orthodontics, is a centuries old practice. Over the decades, continuous discourse and controversy have circulated among orthodontic practitioners, scientists and researchers regarding the movement and extraction of human teeth. In 1901 orthodontic pioneer Edward Angle lead the industry in advocating an uncompromising position staunchly against the extraction of teeth to alleviate dental crowding, malalignment, or bite related (i.e., occlusal) problems. Conversely, Calvin Case and others in the industry at that time were vocal proponents of tooth extraction therapy. Heated debate regarding the pros and cons of tooth extractions as a treatment strategy continues vigorously to this day.
As time passed, and the use of tooth extraction therapy proliferated in the industry during the early and mid-1900s, practitioners began documenting orthodontic extraction cases that culminated in compromised patient profiles, highlighted by patients demonstrating insufficient lip support for optimal facial aesthetics. Consequently, the practitioners' pendulum began to swing back toward Dr. Angle's practice philosophy against the use of tooth extraction therapy as a primary strategy to address patient occlusal scenarios. Practitioners and other industry participants began employing a more thoughtful approach to diagnostic and treatment planning involving tooth extraction therapy.
The gradual decline in employing tooth extraction strategies coincided with increased practitioner efforts to identify innovative appliances capable of moving, as opposed to extracting, human teeth. Many tooth movement appliances at this time were attached to teeth surfaces and various forms of force were applied to the attached appliances in order to effectuate desired movement. Conventional sources of force involved the use of springs and wires to apply force to dental appliances attached to a patient's teeth. Of interest to aligner technology is the use of rubberized teeth aligners, commencing in the late 1800s, made from a material called vulcanite, which was formed over plaster teeth models and subsequently delivered to the patient's dentition to cause desired tooth movement.
In 1942, an apparatus called the Edgewise appliance was introduced into the marketplace. This appliance incorporated stainless steel brackets with milled rectangular edgewise slots to house orthodontic wires. These brackets were welded to stainless steel bands that were then cemented onto a patient's teeth. In the 1970s, several key publications and new dental appliances emerged disclosing tooth movement techniques that ultimately became industry standards in the field of Orthodontic Biomechanics. One such appliance was the Straight Wire Appliance, which incorporated specific angles milled into bracket slots so that rectangular shaped wires could better control the movement of teeth in all three planes of space without having to bend a stainless steel wire at each tooth. This technology was considered by many as a significant orthodontic innovation.
Also during the 1970s, several leading practitioners became increasingly dissatisfied with the finished results of patient cases involving the use of tooth movement technology available at the time. Practitioner dissatisfaction derived from the belief that patient occlusion or bite could be related to symptoms of jaw joint disorder, which practitioners increasingly encountered in the clinical presentation of orthodontic patient cases. These practitioners turned to their dental colleagues in the field of restorative dentistry, who treated patient occlusions with more precision in coordination with jaw muscles and the temporomandibular (jaw) joints (TMJ”).
Subsequently, new systems and refinements of Straight Wire Appliances emerged, which were capable of achieving tooth movement with more precision and predictability. The development of these new technologies is significant because the proponents of these new techniques were early critics of the use of clear plastic aligners to achieve tooth movement. The proponents believed that, while clear plastic aligner appliances may improve teeth alignment, such aligners lacked the capacity to position teeth with the level of precision required to achieve the best and most reliable patient outcomes.
In the late 1970s, an orthodontic treatment philosophy known as Goal Centered Treatment was published and became prevalent in the Orthodontic Biomechanics industry. This philosophy guides practitioners to utilize 7 specific goals in diagnosing and establishing treatment plans for each individual orthodontic case. The 7 specific orthodontic goals are summarized below:
(1) Dental Esthetics: Nicely aligned teeth and a beautiful smile;
(2) Facial Esthetics: A pleasant looking face, where from a profile view the forehead, nose, lips and chin are balanced, and from a frontal view facial symmetry is achieved;
(3) Functional Occlusion: (A) A healthy bite that masticates food comfortably and efficiently, and that will contribute to the longevity of the supporting periodontal (gum) tissues and to dental enamel integrity with regard to wear; (B) Key points of functional occlusion incorporate cuspid rise and anterior guidance whereby cuspids and incisors lift off of the posterior teeth so that stress is taken off of chewing muscles and TMJ joint hard and soft tissue; (C) Minimization of closing prematurities, which are contacts of the teeth during the arc of closure of the jaw initiated in the centered position of the jaw joint (Centric Relation) that lead to distraction of the jaw from the joint as it is translated to the most interdigitated position of the teeth (Centric Occlusion). Many clinicians believe that these movements, commonly referred to as CR/CO slides, are related to TMJ Disorders and jaw joint pain;
(4) Periodontal (Gum Tissue) Health: Over expansion of dental arches may lead to gum tissue recession and exposure of teeth roots;
(5) Healthy Jaw Joint (TMJ): A bite that functions in harmony with the jaw joint and supporting muscles and ligaments;
(6) Stability: Lasting results that are sustainable over time; and
(7) Addressing The Patient's Chief Complaint: Making sure that the patient's primary treatment objectives are achieved and not overlooked or otherwise diminished during orthodontic planning.
As the field of Orthodontic Biomechanics continued to evolve into the 21st Century, practitioners increasingly investigated biologic considerations of tooth movement at the cellular and molecular levels in combination with the pure mechanical forces of dental appliances. Experts in the field investigated the concepts of straight line vector forces, rotational forces (or moments), centers of rotation, centers of resistance, and undesired side effects in applying forces to move teeth.
Orthodontic tooth movement historically occurred with the use of relatively heavy intermittent forces, followed by a biologic response of the patient's teeth, bone, and supporting tissues. Some patient biologic responses were harmful to patients, leading ultimately to necrosis (i.e., tissue death), loss of root integrity, and root resorption. Orthodontist typically employed a biologic repair process, via a time out or recess from treatment, and orthodontic forces were subsequently reapplied. Research conducted during the last decade has revealed that biologically healthy and efficient tooth movement usually occurs with the application of continuous forces in the range of 75 to 200 grams of continuous force.
In evaluating advances in tooth movement technology, a common challenge, that of anchorage, became a primary topic of peer review discourse and clinical research. From a clinical point of view, anchorage involves an orthodontic practitioner's attempt to stabilize (i.e., anchor) patient teeth to diminish tooth movement while applying movement forces to other teeth. Typical anchorage techniques employ headgear, heavy arch wires, trans-palatal arch wires, springs, and later miniature bone screws or temporary anchorage devices (“TADs”), and currently, aligners.
Originally, wires used in orthodontics were fabricated from gold, and then later from stainless steel. Both were useful at the time, but their biological properties had limitations. For instance, gold is relatively soft and expensive. Stainless steel wires generate forces that may exceed the biologic optimum for tooth movement, and their range of action is relatively limited. Modem metallurgy has led to various new age wires, including nickel-titanium alloys and others, which provide measurably more gentle forces over a longer period of time.
Conventional anchorage technology currently involves the use of aligner devices to achieve tooth stabilization. Indeed, the use of clear plastic aligners to move teeth is not a new concept in orthodontics. Conventional aligners have been made from thin, thermoplastic sheets that incorporate clear plastic made from a polyester, polypropenate, or similar material, which is heated to soften and then thermoplastically vacuum-pressed or positive pressure-pressed over plaster models in a dental laboratory. A series of such models were then constructed in the laboratory and reconfigured with small increments of movement of the teeth in plaster models so that a series of aligners would move the teeth in the mouth in a similar fashion. Plastic buttons, similar to conventional attachments or engagers, were used as retentive points oftentimes along with these early aligners. Thermoplastic appliances were also used in the fabrication of temporary crowns in restorative dentistry, vehicles to house dental bleaching material, retainers, athletic mouth guards, and hard splints or night guards for TMJ patients.
At this time in the industry, a clinical methodology did not exist to calculate accurately, or even remotely, the forces placed on teeth by these earlier teeth aligners. Forces were judged primarily by patient reaction upon aligner placement onto a patient's teeth, and gingival tissue blanching if forces were excessive. However, in 1997 two Stanford University MBA graduate students initiated the development of an orthodontic appliance that would revolutionize the profession. Both graduate students were previous orthodontic patients and had personally experienced conventional orthodontic treatment involving bracketed appliances. One of the graduate students noticed that when he did not wear his retainers, his teeth gradually moved, but when he put his clear thermoplastic retainers back into his mouth, his teeth quickly realigned. As a result of their direct patient experience with conventional orthodontic bracketed appliances, the graduate students subsequently worked with Silicon Valley computer programmers to develop three-dimensional imaging graphics software to move teeth virtually in stages. This imaging graphics technology was used to generate a series of aligners from physical plastic models, which included a different patient aligner for each stage of tooth movement. Following the development of this virtual tooth moving imaging graphics technology, other marketplace participants began developing similar software-generated orthodontic appliances.
By the year 2000, digital graphics software products, from various software manufacturers, were available in the marketplace. Initially, the orthodontic community did not fully embrace this imaging graphics technology and related appliances. Some practitioners reported negative experiences involving clinical use of the software and corollary orthodontic appliances. Moreover, these products were marketed directly to the public, which created a significant initial demand, but lacked adequate long-term clinical studies to identify and resolve the clinical presentation of product flaws involving various patient cases. For instance, the first generation of ceramic tooth colored brackets was initially popular in the marketplace, as their esthetic appeal was readily apparent. However, practitioners employing these first generation brackets later discovered that the appliances were also highly abrasive, causing severe enamel wear if opposing teeth came into contact with the ceramic brackets. Also, the corresponding silane-based adhesive system was too strong, leading to patient tooth fracture upon bracket removal.
In addition to the clinical presentation of imaging graphics technology product flaws, an increasing number of practitioners reported concerns regarding the future impact that these products may have on the credibility and efficacy of the practice of Orthodontic Biomechanics. Because orthodontists were initially resistant to embracing imaging graphics tooth movement technology, companies began marketing these products directly to general dentists. Consequently, a significant segment of the tooth movement market was lost to general dentist providers, producing numerous patient outcomes that were substantially less than desirable. While general practitioners were able to achieve some level of tooth movement employing imaging graphics technology, precise three-dimensional tooth positioning was commonly not achieved. A substantial number of patient cases did not meet industry standards, and imaging graphics technology suffered harsh criticism. These circumstances corroborated practitioner concerns that directly marketing imaging graphics technology products to the public could result in establishing a cookbook system for generating tooth movement, which would obviate the application of specialized orthodontic tooth movement treatment in the marketplace. The core concern was that the expertise required to achieve effective, reliable and reproducible tooth movement patient outcomes would be increasingly relegated by a cookbook tooth movement system that practically anybody could provide. Orthodontists and other experts in the field of Orthodontic Biomechanics continue to advocate the position that effective tooth movement remains both an art and a science, and those orthodontic specialists trained in achieving desired patient tooth movement outcomes are best suited to deliver such services.
Over time, a small group of noteworthy orthodontists began working closely with biomechanical engineers in the aligner systems industry to refine existing aligner systems and render them capable of moving teeth according to industry standards. The general hypothesis was that as brackets were merely tools to move teeth to specific positions in the three dimensions of space, so too could aligner system tools be refined to move teeth in a similar fashion. The key objectives in this regard were to define clearly patient goals, and correspondingly develop techniques and methodologies to achieve patient goals employing aligner systems.
To this end, prospective aligner system innovations involved the following well established three dimensional tooth movement components:                Torque is the tipping of a tooth in the buccal-labial/lingual and buccal-labial/palatal direction (cheek side/tongue side or cheek side/palate side). If the center of rotation is on the crown of the tooth, the torque is referred to as either “labial (or buccal) root torque” or if in the opposite direction “palatal (or lingual) root torque”. If the center of rotation is about the root apex, the torque is referred to as crown torque. In reality, the center of rotation is usually not at either the crown or root apex and torqueing movements result in both movement of the crown and the roots, at least with bracketed appliances;        Angulation is the tipping of teeth in a mesial/distal direction (forward/backward at the contact points);        Rotation is the circular or twisting movement (a moment force) about the long axis of the root and crown of the tooth. This is the straightening of crooked teeth;        Bodily Movement is the movement of the whole tooth through bone with little or no tipping, torqueing, or rotation of the tooth. In bracketed orthodontic treatment this is accomplished with a combination of both straight line vector forces and moment (rotational) forces. In reality, true bodily movement rarely, if ever, occurs in orthodontics. Teeth move along a rigid arch wire with small tipping movements and periods of recovery;        Intrusion is the movement of teeth towards the apex of the root;        Extrusion is the movement of teeth in the opposite direction, i.e. towards the crown of the tooth; and        Anchorage is the stabilization or one or more teeth to resist a reciprocal force and movement while applying a force to move other teeth.        
Aligner systems have for several years used small bits of plastic or composite material bonded to teeth to help retain aligners with undercuts that act as purchase points upon which tooth movement forces are applied. The composite material components were referred to as attachments, buttons, engagers, and other similar names particular to manufacturers. Early attachment designs were usually round or ovoid in shape with rounded top surfaces. A frequently encountered problem with aligner systems employing conventional attachments is that varying tooth surfaces often provide insufficient contoured surface area onto which the attachments and corresponding aligners can adhere securely. Consequently, such aligners often cannot adhere to teeth without slipping.
In addition, a significant level of frustration exists in the marketplace regarding the fabrication, placement, and effectiveness of attachments used in conjunction with conventional aligner systems. Currently available aligner technologies do not provide a predictable, reliable system or method for precise attachment fabrication or placement. From a practitioner's point of view, it is critical for the success and efficacy of these attachments and engagers that they are precisely applied to the tooth in the same shape and form as intended, without distortion. However, current attachment placements techniques are significantly technique sensitive. Application of the attachments is often delegated to dental auxiliaries who have varying levels of skill and consistency in their technique. They may also choose whatever composite material they have available, from highly filled to lightly filled with large or small particle sizes, or unfilled altogether. The choice of material for the attachments makes a significant difference in the long-term integrity of the attachment and its fit with corresponding aligners.
Further, if either too much or too little pressure is placed on the attachment template by the clinician during fabrication, the attachment can be greatly distorted. If too much composite is placed in the attachment template, a great deal of excess composite or “flash” will result. Flash can negatively affect aligner fit, and can lead to a negative patient experience during flash removal by the clinician. Clinician attempts to shape up attachments after placement can further distort attachments, and occasionally attachments can have voids as a result of poor placement technique. All of these shortcomings in technique cause what was intended as precision attachment to become imprecise and inconsistent. In practice, attachment placement is consistently inconsistent.
The results of imprecise attachment fabrication and placement include: less efficient tooth movement due to poor engagement of the aligner tray with the attachment; more mid-course corrections and refinements; longer treatment times; lower profits for both the doctors and the aligner companies; more difficulty for patients, and therefore less positive patient experiences; and inaccurate, imprecise tooth movement outcomes.
Information relevant to attempts to address tooth movement technologies can be found in U.S. Pat. No. 7,585,172 issued to Rubbert et al. entitled Orthodontic Treatment Planning With User-Specified Simulation Of Tooth Movement; U.S. Pat. No. 7,188,421 issued to Cleary et al. entitled Orthodontic Appliances Having A Contoured Bonding Surface; U.S. Pat. No. 7,020,963 issued to Cleary et al. entitled Method And Apparatus For Indirect Bonding Of Orthodontic Appliances; U.S. Patent Application Publication No. 2012/0150494 by Anderson et al. entitled Orthodontic Aligner Fabrication By Overlay Method; U.S. Pat. No. 7,845,938 issued to Kim et al. entitled Indirect Bonding Trays For Orthodontic Treatment And Methods For Making The Same; U.S. Pat. No. 7,476,100 issued to Kuo entitled Guide Apparatus And Methods For Making Tooth Positioning Appliances; U.S. Patent Application Publication No. 2010/0138025 entitled Orthodontic Systems And Methods Including Parametric Attachments; U.S. Patent Application Publication No. 2011/0020761 by Kalili entitled Orthodontic Repositioning Appliance; U.S. Pat. No. 6,250,918 issued to Sachdeva et al. entitled Method And Apparatus For Simulating Tooth Movement For An Orthodontic Patient; and U.S. Patent Application Publication No. 2005/0074716 by Cleary et al. entitled Apparatus For Indirect Bonding Of Orthodontic Appliances And Method Of Making The Same.
However, each one of the previously mentioned references suffers from one or more of the following disadvantages. The referenced systems, methods and devices lack sufficient capacity to effectuate precise tooth movement in a clinically reliable and reproducible manner. The disclosed technology does not adequately resolve the problem of an increased need for mid-course corrections and refinements due to inaccurate attachment placement, and lengthy treatment times associated with imprecisely placed attachments. The disclosed technology also fails to address problems involving flash resulting from attachment placement, which may lead to patient discomfort during flash removal, imprecise aligner retention, and longer term periodontal disease.
For the foregoing reasons, a need exists for a method and apparatus to achieve accurate attachment fabrication and placement. In order for attachments to function effectively and produce desired patient outcomes, they must be applied to teeth with precision and minimal distortion due to variable such as practitioner technique, pressure variations applied to attachment templates, and overuse of composite applied to attachment templates resulting in undesirable excess, or flash. Flash is undesirable as its presence can hamper attachment fit and create patient discomfort during flash removal. In addition, flash can create rough edges around placed attachments, which can irritate patient gingival tissue and attract dental plaque, leading to oral hygiene problems and gingival tissue inflammation. Ultimately, flash can lead to gingival or gum tissue redness, swelling and inflammation, bleeding, pain, or halitosis. Composite flash can also form unsightly stains from certain foods, coffee, tea and smoking.
Application of the disclosed invention will result in the fabrication and placement of more precise attachments, and correspondingly more reliable purchase points for teeth to which tooth movement forces may be applied.